1. Field of the Invention
The present invention relates to a method for manufacturing a lithium-containing composite oxide. The present invention also relates to a lithium-ion secondary battery including an electrode in which a lithium-containing composite oxide is used as an active material.
2. Description of the Related Art
In recent years, lithium-ion secondary batteries have been developed. Because of their high thermal stability, lithium-containing composite oxides having olivine structures, such as LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4, have been expected as positive electrode active materials of lithium-ion secondary batteries. Such a lithium-containing composite oxide having an olivine structure contains a bivalent transition metal element (e.g., Fe, Mn, Co, and Ni).
As a method for manufacturing lithium-containing composite oxides having olivine structures, a solid phase method, a hydrothermal method, a sol-gel method, or the like is employed (e.g., Patent Document 1).
In order to increase the discharge capacity and the energy density of lithium-ion secondary batteries, attempts have been made to reduce the particle diameters and variation in particle size of active materials included in an active material layer that relates to intercalation and deintercalation of ions functioning as carriers. A hydrothermal method has been used as a method for manufacturing lithium-containing composite oxides with less variation in particle size and small particle diameters. In a hydrothermal method, a solution obtained by dissolving raw materials of a source of lithium, a source of a bivalent transition metal element, and a source of phosphorus in water is put into a heat-resistant container and heated to a predetermined temperature so that synthetic reaction is caused.